Double-heat-pump drying system and control method thereof

Abstract

The invention belongs to the technical field of heat pumps, and particularly relates to a double-heat-pump drying system and a control method thereof.The double-heat-pump drying system comprises a compressor, a first heat pump, a second heat pump, a first heat pump and a second heat pump, the external evaporator is arranged outside the circulating air duct, an inlet of the external evaporator is connected with an outlet of the condenser, an outlet of the external evaporator is connected with an air suction port of the first air cylinder, the internal evaporator is located in the circulating air duct, an inlet of the internal evaporator is connected with an outlet of the condenser, and an outlet of the internal evaporator is connected with an air suction port of the second air cylinder. According to the double-heat-pump drying system and the control method thereof, by combining the design of external fresh air and the double-air-suction single-exhaust compressor and through mutual cooperation of the double evaporators, the temperature of the system can be rapidly increased in the initial stage, the drying speed is increased, and the drying efficiency is improved. And the optimization of the system structure and the improvement of the environmental adaptability are realized.

Description

Technical Field

[0001] This invention belongs to the field of heat pump technology, and particularly relates to a dual heat pump drying system and its control method. Background Technology

[0002] Currently, mainstream heat pump drying systems are mainly divided into two categories: open systems and closed systems. The open-type heat pump drying system works as follows: the outdoor evaporator absorbs heat from the environment, and then transfers this heat to the drying chamber through the indoor condenser to meet the drying requirements. The core advantage of this system is its strong adaptability, but its disadvantages are equally prominent. During operation, it needs to directly exhaust the high-temperature, high-humidity air generated inside the drying chamber to the outside to achieve dehumidification. This process not only wastes a significant amount of heat and reduces energy efficiency but may also have a certain impact on the surrounding environment. The closed-type heat pump drying system uses a different circulation mode: the humid air inside the drying chamber first passes through the evaporator for cooling and dehumidification, and then the dehumidified air enters the condenser to be heated and reused for the drying operation. The key advantage of this system is its high energy recovery efficiency, which can effectively recover the latent heat load in the humid air and reduce energy loss. Against the backdrop of the increasing demand for energy-efficient home appliances, the closed-type heat pump drying system, with its core advantages of high energy recovery efficiency and low energy consumption, is gradually becoming the focus of market attention. Its characteristic of not needing to exhaust high-temperature, high-humidity air to the outside also makes it more adaptable to residential environments than traditional open-type models. However, in practical applications, the current mainstream closed-loop heat pump drying systems still have room for improvement in three key dimensions: system optimization, drying efficiency, and environmental adaptability, which to some extent affects the user experience. First, from the perspective of system optimization and environmental adaptability, traditional closed-loop heat pump drying systems generally have two significant shortcomings: one is the lack of a mechanism for utilizing heat from the external environment, relying solely on internal system circulation for heat exchange, failing to leverage ambient temperature to improve energy efficiency, and easily leading to high energy consumption; the other is the lack of flexibility in the design and adjustment of core components. On the one hand, the evaporator layout often adopts a fixed structure, failing to optimize the heat exchange path according to the airflow distribution within the drying chamber, resulting in limited heat exchange efficiency. On the other hand, the compressor displacement is often fixed, unable to dynamically adjust the output power according to the dryness of the clothes and the drying stage, easily leading to imbalances such as "overpowered" or "insufficient power". Regarding drying efficiency, the high moisture content in the initial stage of drying clothes becomes a key limiting factor. At this stage, the high moisture content of the clothes causes them to absorb a large amount of heat for evaporation when in contact with the air in the air duct, severely slowing down the temperature rise rate of both the air and the clothes themselves. This results in excessively long heating time in the early stages of drying. This delayed heating directly lengthens the overall drying cycle, especially when dealing with large items or batches of clothing, where the extended drying time is more pronounced. This not only reduces ease of use but also, to some extent, negates its energy-saving advantages.

[0003] In view of this, the present invention proposes a dual heat pump drying system and its control method that can utilize external ambient heat to rapidly raise the system temperature in the early stage of drying and accelerate the drying speed. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned technical problems by providing a dual heat pump drying system and its control method. Through optimization of the system structure layout and control process, the system can be rapidly heated in the early stage of drying by utilizing external ambient heat, thereby accelerating the drying speed.

[0005] In view of this, the present invention provides a dual heat pump drying system, comprising: The compressor includes a first cylinder and a second cylinder, wherein the displacement of the first cylinder is smaller than the displacement of the second cylinder. A condenser, the inlet of which is connected to the exhaust port of the compressor; as well as, An external evaporator and an internal evaporator are provided. The external evaporator is located outside the circulating air duct, and its inlet is connected to the outlet of the condenser through a first throttling device. Its outlet is connected to the air intake of the first cylinder. It is used to absorb heat from the external ambient air through evaporation. The internal evaporator is located in the circulating air duct, and its inlet is connected to the outlet of the condenser through a second throttling device. Its outlet is connected to the air intake of the second cylinder. It is used to recover heat from the humid air generated during the drying process and to dehumidify the humid air. A first throttling device and a second throttling device, the first throttling device being connected to the inlet of the external evaporator and the second throttling device being connected to the inlet of the internal evaporator, are used to regulate the refrigerant flow rate and pressure entering the external evaporator and the internal evaporator.

[0006] Furthermore, the exhaust ports of both the first cylinder and the second cylinder are connected to the inner cavity of the compressor housing and share a common exhaust channel, forming a dual-intake, single-exhaust structure.

[0007] Furthermore, the external evaporator is located outside the entire dual heat pump drying system.

[0008] Furthermore, the dual heat pump drying system also includes: An external fan, used to drive outside air to flow through the external evaporator; An internal fan, which is installed in the circulating air duct, is used to drive the air in the circulating air duct to flow through the internal evaporator and condenser.

[0009] Furthermore, the dual heat pump drying system also includes a filter, which is disposed on the air inlet side of the internal evaporator to filter the circulating air entering the internal evaporator.

[0010] The present invention also provides a control method for a dual heat pump drying system, the control method being used in the aforementioned dual heat pump drying system, the control method comprising the following steps: The dual heat pump drying system is turned on and begins the drying process; The system determines whether to enter dual-evaporation mode: If so, the system operates in dual evaporation mode: the first throttling device, the second throttling device, the external fan and the internal fan are all turned on. The external evaporator absorbs heat from the ambient air, and the internal evaporator recovers heat from the humid air generated during the drying process and dehumidifies the humid air. If not, the system operates in single evaporation mode: the first throttling device and the external fan are turned off, causing the external evaporator to stop working, while the second throttling device and the internal fan remain on, and the internal evaporator continues to work to dehumidify the hot and humid air.

[0011] Furthermore, during system operation in dual evaporation mode, the evaporation temperature T at the external evaporator is monitored in real time. e and external ambient temperature T h And calculate the external ambient temperature T h and evaporation temperature T e The difference, if T h -T e If the temperature is ≤b℃, where b℃ is a preset temperature threshold, the control system switches to single evaporation mode.

[0012] Furthermore, when the dual heat pump drying system starts executing the drying program, it first uses a temperature sensor to detect the current external ambient temperature T in real time. h When the ambient temperature T is detected h When the temperature is ≥a℃, where a℃ is a preset temperature threshold, the dual heat pump drying system is controlled to enter the dual evaporation mode.

[0013] Furthermore, if the ambient temperature T is detected... h If the temperature is less than a℃, the dual heat pump drying system will be directly controlled to enter single evaporation mode.

[0014] Furthermore, when the dual heat pump drying system first enters the dual steam mode, the first throttling device, the second throttling device, the external fan and the internal fan are turned on first, and the compressor is controlled to start after a delay of t seconds. When the dual heat pump drying system finishes drying and stops operating, the compressor is turned off first, and then the internal fan is turned off after a delay of t seconds. The value of t is 5 to 15 seconds.

[0015] The beneficial effects of this invention are: This invention provides a dual heat pump drying system and its control method capable of rapid temperature rise. By combining external fresh air, a dual-cylinder compressor, an external evaporator, and an internal evaporator, the system achieves a rapid increase in drying temperature during the initial operation phase. Compared to existing technologies, it offers the following significant advantages: 1. Rapid heating: By combining external fresh air and a dual-intake, single-exhaust compressor design, the heat pump drying system can absorb heat from the outside air using the external evaporator in the initial stage of operation, while simultaneously recovering heat from the air flowing out of the drying chamber, such as the drum, using the internal evaporator. The cooperation between the two evaporators enables the system to heat up rapidly in the initial stage, accelerating the drying speed.

[0016] 2. Effective utilization of external heat: The dual heat pump drying system of the present invention uses the cooperation of a dual-cylinder compressor and dual evaporators to place the external evaporator outside the circulating air duct. The external evaporator exchanges heat with the outside air, so as to absorb heat from the outside air in the initial stage of drying and increase the temperature of the circulating air in the circulating air duct, thus effectively utilizing external heat.

[0017] 3. System optimization and improved environmental adaptability: The dual heat pump drying system described in this invention fills the gap in the existing heat pump drying system's mechanism for utilizing heat from the external environment, achieving the goal of improving energy efficiency with the help of ambient temperature; at the same time, the layout of the evaporator and compressor is reasonable and the coordination method is flexible, which can be adjusted according to specific working conditions, and has the advantages of flexibility and strong adaptability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the operation mode of the dual heat pump drying system described in this invention when operating in dual evaporation mode; Figure 2 This is a schematic diagram of the operation mode of the dual heat pump drying system described in this invention when operating in single evaporation mode; Figure 3 This is a schematic diagram of the control method of the dual heat pump drying system described in this invention; The markings in the diagram are as follows: 1. Compressor; 101. First cylinder; 102. Second cylinder; 2. Condenser; 3. External evaporator; 4. Internal evaporator; 5. Circulating air duct; 6. Filter; 7. First throttling device; 8. Second throttling device. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] In the description of this application, it should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0021] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0022] like Figures 1-2 As shown, a dual heat pump drying system includes: Compressor 1 is a dual-cylinder compressor including a first cylinder 101 and a second cylinder 102, wherein the displacement of the first cylinder 101 is smaller than the displacement of the second cylinder 102. Condenser 2, the inlet of which is connected to the exhaust port of compressor 1; as well as, An external evaporator 3 and an internal evaporator 4 are provided. The external evaporator 3 is located outside the circulating air duct 5 of the dual heat pump drying system. Its inlet is connected to the outlet of the condenser 2 through a first throttling device 7, and its outlet is connected to the air intake of the first cylinder 101. It is used to absorb heat from the external ambient air through evaporation. The internal evaporator 4 is located in the circulating air duct 5 of the dual heat pump drying system. Its inlet is connected to the outlet of the condenser 2 through a second throttling device 8, and its outlet is connected to the air intake of the second cylinder 102. It is used to recover heat from the humid air generated during the drying process and to dehumidify the humid air. A first throttling device 7 and a second throttling device 8 are used to regulate the flow rate and pressure of the refrigerant entering the external evaporator 3 and the internal evaporator 4, respectively.

[0023] Specifically, the condenser 2 in the dual heat pump drying system of the present invention is used to condense the high-temperature and high-pressure gaseous refrigerant discharged by the compressor 1 into a subcooled liquid refrigerant, and transfer the heat to the air in the circulating air duct 5 to achieve heating and temperature rise of the air in the circulating air duct 5.

[0024] Preferably, the exhaust ports of the first cylinder 101 and the second cylinder 102 in the compressor 1 are both connected to the inner cavity of the compressor 1 housing and share a common exhaust channel, forming a dual-intake single-exhaust structure.

[0025] As a preferred example of the present invention, the external evaporator 3 is disposed outside the dual heat pump drying system, that is, between the entire dual heat pump drying system and the environment. Specifically, the external evaporator 3 can be integrally disposed outside the entire dual heat pump drying system, or the external evaporator 3 and the entire dual heat pump drying system can be disposed in different locations, such as the entire dual heat pump drying system being disposed indoors and the external evaporator 3 being disposed outdoors, and connected to the compressor 1 and condenser 2 via refrigerant delivery pipes. Here, the entire dual heat pump drying system refers to the relatively independent and complete main equipment unit integrated by the drying system to achieve the core drying function.

[0026] In this invention, the external evaporator 3 is positioned between the whole machine and the environment. Its position is designed so that the external evaporator 3 can fully contact the air entering from the outside, thereby improving the heat absorption efficiency and facilitating the absorption of external heat by the external evaporator 3.

[0027] Furthermore, the dual heat pump drying system also includes: An external fan is used to drive outside air to flow through the external evaporator 3; An internal fan is installed inside the circulating air duct 5 to drive the air in the circulating air duct 5 to flow through the internal evaporator 4 and condenser 2.

[0028] As some examples of the present invention, the external fan can be installed on the air inlet side or air outlet side of the external evaporator 3, and the internal fan can be installed on the air outlet side of the condenser 2.

[0029] As a preferred example of the present invention, the first throttling device 7 and the second throttling device 8 can be configured as electronic expansion valves, thereby adjusting the opening degree of the expansion valve according to different ambient temperatures to achieve precise control of the operating parameters of the compressor 1.

[0030] As a preferred example of the present invention, the dual heat pump drying system further includes a filter 6, which is disposed on the air inlet side of the internal evaporator 4 to filter the circulating air entering the internal evaporator 4 and prevent materials such as lint from entering the internal evaporator 4.

[0031] Of course, it is understood that the dual heat pump drying system described in this invention should also include a control system, which includes components such as a controller and a temperature sensor, and the control system is able to control the components therein to operate in a set manner.

[0032] Specifically, the control system can be used to monitor the operating status of the dual heat pump drying system in real time, and dynamically adjust the opening and closing of the throttling device and the fan according to the drying stage.

[0033] In addition, such as Figure 3 As shown, the present invention also provides a control method for a dual heat pump drying system, the control method being used in the aforementioned dual heat pump drying system, the control method comprising the following steps: The dual heat pump drying system is turned on and begins the drying process; The system determines whether to enter dual-evaporation mode: If so, the system operates in dual evaporation mode. At this time, the first throttling device 7, the second throttling device 8, the external fan and the internal fan are all turned on. The external evaporator 3 absorbs heat from the ambient air, and the internal evaporator 4 recovers heat from the humid air generated during the drying process and dehumidifies the humid air. If not, the system operates in single evaporation mode. In this case, the first throttling device 7 and the external fan are turned off, so that the external evaporator 3 stops working. The second throttling device 8 and the internal fan remain on, and the internal evaporator 4 continues to work to dehumidify the hot and humid air. Preferably, when the dual heat pump drying system starts executing the drying program, it can first determine whether to enter the dual evaporation mode based on the current ambient temperature. The specific determination process is as follows: First, the current external ambient temperature T is detected in real time by a temperature sensor.h When the ambient temperature T is detected h ≥a℃, where a℃ is a preset temperature threshold. At this time, it is proven that the heat from the external fresh air can be used to provide heat to the external evaporator 3. Then, the first throttling device 7 and the second throttling device 8 are turned on, and the external fan and the internal fan are turned on at the same time to control the dual heat pump drying system to enter the dual evaporation mode.

[0034] However, if the ambient temperature T is detected... h If the temperature is less than a℃, it indicates that the external ambient temperature is too low. At this time, it is difficult to effectively utilize the heat from the external fresh air to provide heat to the external evaporator 3. It is not advisable to control the dual heat pump drying system to enter the dual evaporation mode. In this case, the dual heat pump drying system can be directly controlled to enter the single evaporation mode.

[0035] More preferably, when the dual heat pump drying system just enters the dual steam mode, the first throttling device 7, the second throttling device 8, the external fan and the internal fan can be turned on first, and the compressor 1 can be turned on after a delay of t seconds. That is, the compressor 1 is started after the first throttling device 7, the second throttling device 8, the external fan and the internal fan are turned on for t seconds, so as to prevent the air from not flowing and thus deteriorating the heat transfer when the compressor 1 is running.

[0036] As a preferred example of the present invention, when the dual heat pump drying system just enters the drying program, the current external ambient temperature T is detected in real time by a temperature sensor. h When the ambient temperature T is detected h The condition T is satisfied for n consecutive seconds. h When the temperature is ≥a℃, the dual heat pump drying system is controlled to enter dual evaporation mode.

[0037] Furthermore, during the operation of the system in the dual evaporation mode, the system can detect the evaporation temperature T at the external evaporator 1 in real time. e and external ambient temperature T h And based on the evaporation temperature T e and external ambient temperature T h Determine whether to end the dual evaporation mode, i.e., whether the initial drying stage or the drying temperature rise has ended, and then switch the system to single evaporation mode.

[0038] As some examples of the present invention, based on the evaporation temperature T e and external ambient temperature T h The method to determine whether to end the dual evaporation mode is: calculate the external ambient temperature T. h and evaporation temperature T e The difference, if T h -T eIf the temperature is ≤b℃, where b℃ is a preset temperature threshold, then the first throttling device 7 and the external fan are shut off, causing the external evaporator 3 to stop working, and the control system switches to single evaporation mode. Otherwise, it indicates that the system has not yet completed the drying and heating process and still needs to operate in dual evaporation mode.

[0039] Preferably, when switching modes, the external ambient temperature T can be monitored. h and evaporation temperature T e The value of T is continuously detected. If T is detected continuously for n seconds... h -T e If the temperature is ≤b℃, the drying and heating stage ends, the control system switches to single evaporation mode and continues to execute the conventional condenser 2 heating and internal evaporator 4 dehumidification functions.

[0040] As a preferred example of the present invention, when the dual heat pump drying system finishes drying and ends operation, compressor 1 can be turned off first, and then the internal fan can be turned off after a delay of t seconds.

[0041] Preferably, the delay time t seconds in this invention is 5 to 15 seconds, such as 10 seconds.

[0042] Preferably, the preset temperature threshold a in this invention can be set to 20~28℃, such as 25℃; the preset temperature threshold b can be set to 1~5℃, such as 3℃.

[0043] In the control method of the dual heat pump drying system described in this invention, during the initial drying stage, both the first throttling device 7 and the second throttling device 8 are activated. At this time, the external evaporator 3 absorbs external heat, while the internal evaporator 4 dehumidifies the circulating air inside the system and recovers heat. This dual approach rapidly increases the heat of the heat pump system, causing the drying temperature to rise quickly and accelerating the drying speed. After the drying temperature rise is completed, the first throttling device 7 and the external fan are turned off, the external evaporator 3 stops working, and the internal evaporator 4 continues to dehumidify. In this way, the external evaporator 3 can absorb ambient heat in the early stage of drying, while the internal evaporator 4 cools and dehumidifies the circulating air. The cooperation of the two evaporators allows the system to rapidly heat up in the early stage of drying, accelerating the drying speed.

[0044] Therefore, this invention proposes a dual heat pump drying system with a fresh air system and a dual-cylinder compressor. The dual-cylinder compressor consists of a small-displacement cylinder and a large-displacement cylinder. During the drying and heating stage, the small-displacement cylinder and the large-displacement cylinder of the dual-cylinder compressor are connected to the external evaporator 3 and the internal evaporator 4, respectively. At this time, the external evaporator 3 absorbs ambient heat, and the internal evaporator 4 recovers heat from the exhaust air of the drying chamber. After the drying and heating stage is completed, the system further optimizes the operating mode by shutting down the throttling device and the external fan connected to the external evaporator 3, so that the internal evaporator 4 can continue to dehumidify efficiently. This achieves efficient operation of the system and improves energy utilization. Ultimately, this design achieves the goal of rapid heating in the early stage of drying, effectively shortening the drying time and improving the user experience.

[0045] Furthermore, this invention connects a small-displacement first cylinder 101 to the external evaporator 3, and a large-displacement second cylinder 102 to the internal evaporator 4. Since the small-displacement first cylinder 101 handles a relatively small refrigerant flow rate, and the ambient temperature of the external evaporator 3 is relatively stable with less difficulty in heat acquisition, the small-displacement cylinder is sufficient to meet its refrigerant compression requirements. This avoids the "overkill" phenomenon that might occur when the large-displacement cylinder handles the refrigerant in the external evaporator 3, thereby reducing energy consumption. Simultaneously, the large-displacement cylinder connected to the internal evaporator 4 can fully utilize the large amount of humid air heat recovered by the internal evaporator 4. Because the internal evaporator 4 recovers abundant heat, the large-displacement cylinder can better handle a large amount of refrigerant, efficiently transferring this heat to the drying cycle and improving energy utilization.

[0046] As some examples of the present invention, the dual heat pump drying system can be used in clothing processing equipment such as washing machines, dryers, and washer-dryer combos.

[0047] In summary, this invention provides a dual heat pump drying system and its control method capable of rapid temperature rise. By combining external fresh air, a dual-cylinder compressor 1, an external evaporator 3, and an internal evaporator 4, the heat pump drying system achieves a rapid increase in drying temperature during the initial operation phase. Compared to existing technologies, it has the following significant advantages: 1. Rapid heating: By combining external fresh air and a dual-intake single-exhaust compressor design, the heat pump drying system can absorb heat from the outside air using the external evaporator 3 in the initial stage of operation, while recovering heat from the air flowing out of the drying chamber such as the drum using the internal evaporator 4. The cooperation between the two evaporators enables the system to heat up rapidly in the initial stage, accelerating the drying speed.

[0048] 2. Effective utilization of external heat: The dual heat pump drying system of the present invention uses the cooperation of a dual-cylinder compressor and dual evaporators to place the external evaporator 3 outside the circulating air duct 5. The external evaporator 3 exchanges heat with the outside air, so as to absorb heat from the outside air in the early stage of drying and increase the temperature of the circulating air in the circulating air duct 5, thus effectively utilizing external heat.

[0049] 3. System Optimization and Enhanced Environmental Adaptability: The dual heat pump drying system described in this invention fills the gap in the existing heat pump drying system's mechanism for utilizing external environmental heat, achieving the goal of improving energy efficiency with the assistance of ambient temperature. Simultaneously, the layout of the evaporator and compressor 1 is reasonable, and their coordination is flexible, allowing for adjustments according to specific operating conditions, thus possessing the advantages of flexibility, adjustability, and strong adaptability. The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application is not limited to the specific embodiments described above; the specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art, under the guidance of this application, can make many other forms without departing from the spirit and scope of the claims, all of which fall within the protection scope of this application.

Claims

1. A dual heat pump drying system, characterized in that, include: The compressor (1) includes a first cylinder (101) and a second cylinder (102), wherein the displacement of the first cylinder (101) is smaller than the displacement of the second cylinder (102); The condenser (2) has its inlet connected to the exhaust port of the compressor (1); as well as, An external evaporator (3) and an internal evaporator (4) are provided. The external evaporator (3) is located outside the circulating air duct (5). Its inlet is connected to the outlet of the condenser (2) through a first throttling device (7), and its outlet is connected to the air intake of the first cylinder (101). It is used to absorb heat from the external ambient air through evaporation. The internal evaporator (4) is located in the circulating air duct (5). Its inlet is connected to the outlet of the condenser (2) through a second throttling device (8), and its outlet is connected to the air intake of the second cylinder (102). It is used to recover heat from the humid air generated during the drying process and to dehumidify the humid air. A first throttling device (7) and a second throttling device (8) are provided. The first throttling device (7) is connected to the inlet of the external evaporator (3), and the second throttling device (8) is connected to the inlet of the internal evaporator (4). These devices are used to regulate the flow rate and pressure of the refrigerant entering the external evaporator (3) and the internal evaporator (4).

2. The dual heat pump drying system according to claim 1, characterized in that, The exhaust ports of the first cylinder (101) and the second cylinder (102) are both connected to the inner cavity of the compressor (1) housing and share a common exhaust channel, forming a double intake and single exhaust structure.

3. The dual heat pump drying system according to claim 1, characterized in that, The external evaporator (3) is located outside the entire dual heat pump drying system.

4. The dual heat pump drying system according to claim 1, characterized in that, The dual heat pump drying system also includes: An external fan is used to drive outside air to flow through the external evaporator (3). An internal fan is installed in the circulating air duct (5) to drive the air in the circulating air duct (5) to flow through the internal evaporator (4) and condenser (2).

5. The dual heat pump drying system according to claim 1, characterized in that, The dual heat pump drying system also includes a filter (6) which is located on the air inlet side of the internal evaporator (4) to filter the circulating air entering the internal evaporator (4).

6. A control method for a dual heat pump drying system, characterized in that, The control method is used in the dual heat pump drying system according to any one of claims 1 to 5, and the control method includes the following steps: The dual heat pump drying system is turned on and begins the drying process; The system determines whether to enter dual-evaporation mode: If so, the system operates in dual evaporation mode: the first throttling device, the second throttling device, the external fan and the internal fan are all turned on. The external evaporator absorbs heat from the ambient air, and the internal evaporator recovers heat from the humid air generated during the drying process and dehumidifies the humid air. If not, the system operates in single evaporation mode: the first throttling device and the external fan are turned off, causing the external evaporator to stop working, while the second throttling device and the internal fan remain on, and the internal evaporator continues to work to dehumidify the hot and humid air.

7. The control method for the dual heat pump drying system according to claim 6, characterized in that, During system operation in dual evaporation mode, the evaporation temperature T at the external evaporator is monitored in real time. e and external ambient temperature T h And calculate the external ambient temperature T h and evaporation temperature T e The difference, if T h -T e If the temperature is ≤b℃, where b℃ is a preset temperature threshold, the control system switches to single evaporation mode.

8. The control method for the dual heat pump drying system according to claim 6, characterized in that, When the dual heat pump drying system starts executing the drying program, it first detects the current external ambient temperature T in real time using a temperature sensor. h When the ambient temperature T is detected h When the temperature is ≥a℃, where a℃ is a preset temperature threshold, the dual heat pump drying system is controlled to enter the dual evaporation mode.

9. The control method for the dual heat pump drying system according to claim 8, characterized in that, If the ambient temperature T is detected h If the temperature is less than a℃, the dual heat pump drying system will be directly controlled to operate in single evaporation mode.

10. The control method for the dual heat pump drying system according to claim 6, characterized in that, When the dual heat pump drying system first enters the dual steaming mode, the first throttling device, the second throttling device, the external fan and the internal fan are turned on first, and the compressor is controlled to start after a delay of t seconds. When the dual heat pump drying system finishes drying and stops operating, the compressor is turned off first, and then the internal fan is turned off after a delay of t seconds. The value of t is 5 to 15 seconds.

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